> tapply(watlev, size, mean)
    Small    Medium     Large 
 52.16667 106.43444 152.76654 
> 
> tapply(watlev, swampid, mean)
        1         2         3         4         5         6         7         8 
 48.00037  36.29963  72.20000 110.20185 103.00111 106.10037 128.80000 137.19926 
        9 
192.30037 
> 
> tapply(watlev, swampid, sd)
        1         2         3         4         5         6         7         8 
15.119756 20.840557 20.579668  8.159947 11.429788 15.380268 15.330361 10.289690 
        9 
14.809963 
> 
> swamp.aov1 <- aov(watlev ~ size + size/swampid)
> 
> # This provides ANOVA, not appropriate F-test for fsize
> 
> summary(swamp.aov1)
              Df Sum Sq Mean Sq F value    Pr(>F)    
size           2 410724  205362 888.385 < 2.2e-16 ***
size:swampid   6  83058   13843  59.884 < 2.2e-16 ***
Residuals    234  54092     231                      
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 
> 
> swamp.aov2 <- aov(watlev ~ size + Error(swampid))
> 
> # This provides appropriate F-test for fsize
> 
> summary(swamp.aov2)

Error: swampid
          Df Sum Sq Mean Sq F value   Pr(>F)   
size       2 410724  205362  14.835 0.004759 **
Residuals  6  83058   13843                    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Error: Within
           Df Sum Sq Mean Sq F value Pr(>F)
Residuals 234  54092  231.16               
>